This invention relates generally to a gaseous detection system for detecting the presence and determining the level of a pre-selected gas. One particular application of this system relates to alcohol detection and, more particulary, to the detection of the alcohol or ethanol content of the breath of a person. The blood-alcohol content, as determined by this invention, may be used for evidentiary purposes. The blood-alcohol content may be displayed on a digital read-out system or other methods of display as desired.
It has long been recognized that detection of certain gases is necessary for the safety or well-being of human life. Coal miners used canaries to warn them of the presence of life-endangering gases. The art of gas detection has progressed until today, there are many systems of gas detection (i.e. infrared, gas chromatography, etc.). These systems to date have required costly and elaborate equipment and reference materials to be both accurate and reliable. One primary use for such detection systems has been to detect the presence of breath-alcohol (i.e. ethanol) in the exhalation of a person.
As previously noted in U.S. Pat. No. 4,905,498, issued to Jack O'Donnell, et al., a novel system was developed to use ambient air as the carrier of the gas to be detected. A number of valves and pneumatic pathways were used to control the function of the detection or isolation unit and the functioning of a sensor unit with respect thereto. The comparison operation, carried out in U.S. Pat. No. 4,905,498, made use of a dynamically established reference value that was renewed with each cycle and was referenced to the sensor's operation. This system changed the accuracy of gas sensors using chromatograph tubes to enable accurate readings without the requirement of pure reference gases for carrying the gas to be detected.
The gas detection system of this invention provides an improved, stable analysis of the discernable blood-alcohol content of a person's breath sample displayed on a digital read-out device or ether display mode. The analysis is accurate enough to be used for evidentiary or like purposes.
Although the following description of the best mode relates to the use of the invention in connection with the presence of ethanol in a person's breath, the system, with minor modifications, can also be utilized as a gas detection system for detecting the presence of other selected gases in most environments where such testing is done today.